While many investigators have looked at fragments of the developing phonological system in infants and young children, little work is available which provides an integrated view of phonological language acquisition. An investigation of the development of the perception and production of infants and young children during the first 30 months of life is proposed. This primarily longitudinal study will integrate the results of speech perception and speech production research from infants from two linguistic communities, Spanish and English, into a single framework. Emphasis will be placed on relationships between the developing perceptual system and the developing capacity to produce adultlike utterances. The primary methodologies for study of speech production will be specially modified transcription and categorization systems, as well as acoustic analysis. Methodologies for perception studies will be the VRISD (Visually Reinforced Infant Speech Discrimination) and Shell Game paradigms.